Magnetism magnetic anisotropy

P. Crespo, R. Litran, T. C. Rojas, M. Multigner, J. M. de la Fuente, J. C. Sanchez-Lopez, M. A. Garda, A. Hernando, S. Penades, and A. Fernandez, Permanent magnetism, magnetic anisotropy, and hysteresis of thiol-capped gold nanoparticles, Phys. Rev. Lett., 93 (2004) 087204. 

As a framework for the discussion of the magnetization, magnetic anisotropy and magnetostriction we consider a hamiltonian which comprises the following isotropic exchange, effective single-ion anisotropy, elastic, magnetoelastic and Zeeman terms ... 

Pastor G M, Dorantes-Davila J, Pick S and Dreysse H 1995 Magnetic anisotropy of 3d transition-metal clusters Phys. Rev. Lett. 75 326... 

From the write and read process sketched so far, some requirements for MO media can be derived (/) a high perpendicular, uniaxial magnetic anisotropy K in order to enable readout with the polar Kerr effect (2) a magnetoopticady active layer with a sufficient figure of merit R 0- where R is the reflectivity and the Kerr angle (T) a Curie temperature between 400 and 600 K, the lower limit to enable stable domains at room temperature and the upper limit because of the limited laser power for writing. 

Oriented In-Plane Texture. In this kind of film the properties (H and in the various in-plane directions (texture and nontexture directions) are different. The texture of the film can be supported by the texture of the substrate and the crystal lattice can be smaller in the texture direction than in the transverse direction. This can be the source for strain-induced magnetic anisotropy (magnetostriction). It is also found that the crystal is aligned in the texture direction (92). 

Magnetic Anisotropy Energy. There are several kinds of magnetic anisotropy energy and perhaps the most weU known is the magnetocrystaUine anisotropy. Only a crystalline soHd has this property because the energy is dictated by the symmetry of the crystal lattice. For example, in bcc Fe, the easy axis is in a (100) direction and in fee Ni, it is in a (111) direction. 

Hot pressing to produce substantial texture and magnetic anisotropy via plastic deformation is accompHshed by a process referred to as... 

Tellurium also improves the properties of electrical steels by aiding in the magnetic anisotropy, malleable cast iron (77), and spheroidal (graphitic) cast irons (see also Metal surface TiiEATiffiNTs). 

Figure 1 The principal sources of structural data are the NOEs, which give information on the spatial proximity d of protons coupling constants, which give information on dihedral angles < i and residual dipolar couplings, which give information on the relative orientation 0 of a bond vector with respect to the molecule (to the magnetic anisotropy tensor or an alignment tensor). Protons are shown as spheres. The dashed line indicates a coordinate system rigidly attached to the molecule.

The barium ferrite was found to have an increase in magnetic anisotropy, as in the nickel ferrite, but its overall effect on magnetization was less because of greater magnetocrystalline anisotropy. The shock modification caused reduced crystallite size and local damage that resulted in increased microwave absorption. 

The SH, SCHs, and weakly directing halogens cause small shifts, which to a large extent are determined by magnetic anisotropy effects, especially in the case of the halogens. Attempts have been made to estimate these effects for the other thiophenes. Except for orthohydrogens, these effects are usually very small. 

B. Heinrich and J.F. Cochran, Ultrathin metallic magnetic films magnetic anisotropies and exchange interactions. Advances in Physics 42, 523 (1993). 

The calculation of the magnetic anisotropy of non-cubic materials requires an expansion up to 1 /c . Except in the case of fully relativistic calculations, the expansion is never carried out consistently and only the spin-orbit perturbation is calculated to second order (or to infinite order), without taking account of the other terms of the expansion. In this section, we shall follow Gesztesy et al. (1984) and Grigore et al. (1989) to calculate the terms H3 and H. Hz will be found zero and H4 will give us terms that must be added to the second order spin-orbit calculation to obtain a consistent semi-relativistic expansion. 

I thank P. Bruno for his explanation of the calculation of magnetic anisotropy, and Ph. Sainctavit, L. Varga and D. Cabaret for their thorough readings of the manuscript. 

Chemical applications of magnetic anisotropy studies on transition metal complexes. S. Mitra, Prog. Inorg. Chem., 1977, 22, 310-408 (160). 

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